Access controls are provided on company premises or within a campus environment for security reasons. These access controls are carried out in each case at those points which lead to a secure area or a secure installation. For this purpose it is necessary to install centralized control components which interwork with decentralized control structures.
A representative example of a decentralized access control device is a card reader by which the code of a card introduced into the reader can be read. Once read, the code is usually transmitted to a control center by the card reader. In the control center, the code is checked in respect of its validity for accessing a secure or protected area and if it is verified as being valid, information is transmitted to an opening system. The transmitted information causes the opening system, e.g. a door opener, to be activated and e.g. a person is then able to enter the protected zone. Access controls of this kind are necessary at every access point or access area such as, for example, at every door or barrier or elevator which leads to an area that requires protecting or securing. This means that a fresh access check has to be performed at each of these locations or areas by, for example, a user ID card with access code and card reader.